enable collapsing within AST_Definitions
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alexlamsl
parent
7dd1e0f34b
commit
761792e2e5
236
lib/compress.js
236
lib/compress.js
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@ -647,132 +647,141 @@ merge(Compressor.prototype, {
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for (var stat_index = statements.length; --stat_index >= 0;) {
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var stat = statements[stat_index];
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// The variable definition must precede a statement.
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if (stat_index <= 0) break;
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var prev_stat_index = stat_index - 1;
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var prev_stat = statements[prev_stat_index];
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if (!(prev_stat instanceof AST_Definitions)) continue;
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var var_defs = prev_stat.definitions;
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if (var_defs == null) continue;
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var var_names_seen = {};
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var var_names_seen = Object.create(null);
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var side_effects_encountered = false;
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var lvalues_encountered = false;
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var lvalues = {};
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var lvalues = Object.create(null);
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var prev_stat_index, var_defs, var_defs_index;
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// Scan variable definitions from right to left.
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for (var var_defs_index = var_defs.length; --var_defs_index >= 0;) {
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// Obtain var declaration and var name with basic sanity check.
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var var_decl = var_defs[var_defs_index];
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if (var_decl.value == null) break;
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var var_name = var_decl.name.name;
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if (!var_name || !var_name.length) break;
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// Bail if we've seen a var definition of same name before.
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if (var_name in var_names_seen) break;
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var_names_seen[var_name] = true;
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// Only interested in cases with just one reference to the variable.
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var def = var_decl.name.definition();
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if (def.references.length !== 1
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|| var_name == "arguments" || (!toplevel && def.global)) {
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side_effects_encountered = true;
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continue;
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if (stat instanceof AST_Definitions) {
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prev_stat_index = stat_index;
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var_defs = stat.definitions;
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for (var_defs_index = var_defs.length - 1; --var_defs_index >= 0;) {
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if (collapse(var_defs[var_defs_index + 1])) break;
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}
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var ref = def.references[0];
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// Don't replace ref if eval() or with statement in scope.
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if (ref.scope.uses_eval || ref.scope.uses_with) break;
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// Constant single use vars can be replaced in any scope.
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if (var_decl.value.is_constant()) {
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var ctt = new TreeTransformer(function(node) {
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var parent = ctt.parent();
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if (parent instanceof AST_IterationStatement
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&& (parent.condition === node || parent.init === node)) {
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return node;
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}
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if (node === ref)
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return replace_var(node, parent, true);
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});
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stat.transform(ctt);
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continue;
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} else if (stat_index > 0) {
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// The variable definition must precede a statement.
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prev_stat_index = stat_index - 1;
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var prev_stat = statements[prev_stat_index];
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if (!(prev_stat instanceof AST_Definitions)) continue;
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var_defs = prev_stat.definitions;
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for (var_defs_index = var_defs.length; --var_defs_index >= 0;) {
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if (collapse(stat)) break;
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}
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// Restrict var replacement to constants if side effects encountered.
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if (side_effects_encountered |= lvalues_encountered) continue;
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var value_has_side_effects = var_decl.value.has_side_effects(compressor);
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// Non-constant single use vars can only be replaced in same scope.
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if (ref.scope !== scope) {
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side_effects_encountered |= value_has_side_effects;
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continue;
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}
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// Detect lvalues in var value.
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var tw = new TreeWalker(function(node){
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if (node instanceof AST_SymbolRef && is_lvalue(node, tw.parent())) {
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lvalues[node.name] = lvalues_encountered = true;
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}
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});
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var_decl.value.walk(tw);
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// Replace the non-constant single use var in statement if side effect free.
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var unwind = false;
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var tt = new TreeTransformer(
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function preorder(node) {
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if (unwind) return node;
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var parent = tt.parent();
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if (node instanceof AST_Lambda
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|| node instanceof AST_Try
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|| node instanceof AST_With
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|| node instanceof AST_Case
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|| node instanceof AST_IterationStatement
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|| (parent instanceof AST_If && node !== parent.condition)
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|| (parent instanceof AST_Conditional && node !== parent.condition)
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|| (node instanceof AST_SymbolRef
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&& value_has_side_effects
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&& !are_references_in_scope(node.definition(), scope))
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|| (parent instanceof AST_Binary
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&& (parent.operator == "&&" || parent.operator == "||")
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&& node === parent.right)
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|| (parent instanceof AST_Switch && node !== parent.expression)) {
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return side_effects_encountered = unwind = true, node;
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}
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function are_references_in_scope(def, scope) {
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if (def.orig.length === 1
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&& def.orig[0] instanceof AST_SymbolDefun) return true;
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if (def.scope !== scope) return false;
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var refs = def.references;
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for (var i = 0, len = refs.length; i < len; i++) {
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if (refs[i].scope !== scope) return false;
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}
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return true;
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}
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},
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function postorder(node) {
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if (unwind) return node;
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if (node === ref)
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return unwind = true, replace_var(node, tt.parent(), false);
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if (side_effects_encountered |= node.has_side_effects(compressor))
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return unwind = true, node;
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if (lvalues_encountered && node instanceof AST_SymbolRef && node.name in lvalues) {
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side_effects_encountered = true;
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return unwind = true, node;
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}
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}
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);
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stat.transform(tt);
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}
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}
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return statements;
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function collapse(stat) {
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var var_decl = var_defs[var_defs_index];
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if (var_decl.value == null) return true;
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var var_name = var_decl.name.name;
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if (!var_name || !var_name.length) return true;
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// Bail if we've seen a var definition of same name before.
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if (var_name in var_names_seen) return true;
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var_names_seen[var_name] = true;
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// Only interested in cases with just one reference to the variable.
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var def = var_decl.name.definition();
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if (def.references.length !== 1
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|| var_name == "arguments" || (!toplevel && def.global)) {
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side_effects_encountered = true;
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return;
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}
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var ref = def.references[0];
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// Don't replace ref if eval() or with statement in scope.
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if (ref.scope.uses_eval || ref.scope.uses_with) return true;
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// Constant single use vars can be replaced in any scope.
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if (var_decl.value.is_constant()) {
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var ctt = new TreeTransformer(function(node) {
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var parent = ctt.parent();
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if (parent instanceof AST_IterationStatement
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&& (parent.condition === node || parent.init === node)) {
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return node;
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}
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if (node === ref)
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return replace_var(var_decl, node, parent, true);
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});
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stat.transform(ctt);
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return;
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}
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// Restrict var replacement to constants if side effects encountered.
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if (side_effects_encountered |= lvalues_encountered) return;
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var value_has_side_effects = var_decl.value.has_side_effects(compressor);
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// Non-constant single use vars can only be replaced in same scope.
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if (ref.scope !== scope) {
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side_effects_encountered |= value_has_side_effects;
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return;
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}
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// Detect lvalues in var value.
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var tw = new TreeWalker(function(node){
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if (node instanceof AST_SymbolRef && is_lvalue(node, tw.parent())) {
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lvalues[node.name] = lvalues_encountered = true;
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}
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});
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var_decl.value.walk(tw);
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// Replace the non-constant single use var in statement if side effect free.
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var unwind = false;
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var tt = new TreeTransformer(
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function preorder(node) {
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if (unwind) return node;
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var parent = tt.parent();
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if (node instanceof AST_Lambda
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|| node instanceof AST_Try
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|| node instanceof AST_With
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|| node instanceof AST_Case
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|| node instanceof AST_IterationStatement
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|| (parent instanceof AST_If && node !== parent.condition)
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|| (parent instanceof AST_Conditional && node !== parent.condition)
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|| (node instanceof AST_SymbolRef
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&& value_has_side_effects
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&& !are_references_in_scope(node.definition(), scope))
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|| (parent instanceof AST_Binary
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&& (parent.operator == "&&" || parent.operator == "||")
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&& node === parent.right)
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|| (parent instanceof AST_Switch && node !== parent.expression)) {
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return side_effects_encountered = unwind = true, node;
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}
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function are_references_in_scope(def, scope) {
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if (def.orig.length === 1
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&& def.orig[0] instanceof AST_SymbolDefun) return true;
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if (def.scope !== scope) return false;
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var refs = def.references;
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for (var i = 0, len = refs.length; i < len; i++) {
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if (refs[i].scope !== scope) return false;
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}
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return true;
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}
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},
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function postorder(node) {
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if (unwind) return node;
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if (node === ref)
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return unwind = true, replace_var(var_decl, node, tt.parent(), false);
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if (side_effects_encountered |= node.has_side_effects(compressor))
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return unwind = true, node;
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if (lvalues_encountered && node instanceof AST_SymbolRef && node.name in lvalues) {
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side_effects_encountered = true;
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return unwind = true, node;
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}
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}
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);
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stat.transform(tt);
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}
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function is_lvalue(node, parent) {
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return node instanceof AST_SymbolRef && is_lhs(node, parent);
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}
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function replace_var(node, parent, is_constant) {
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function replace_var(var_decl, node, parent, is_constant) {
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if (is_lvalue(node, parent)) return node;
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// Remove var definition and return its value to the TreeTransformer to replace.
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@ -789,7 +798,7 @@ merge(Compressor.prototype, {
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compressor.info("Collapsing {type} {name} [{file}:{line},{col}]", {
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type: is_constant ? "constant" : "variable",
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name: var_name,
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name: var_decl.name.name,
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file: node.start.file,
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line: node.start.line,
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col: node.start.col
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@ -1737,6 +1746,7 @@ merge(Compressor.prototype, {
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def(AST_SymbolRef, function(compressor){
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return this.undeclared();
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});
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def(AST_SymbolDeclaration, return_false);
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def(AST_Object, function(compressor){
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return any(this.properties, compressor);
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});
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@ -667,7 +667,7 @@ collapse_vars_lvalues: {
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function f4(x) { var a = (x -= 3); return x + a; }
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function f5(x) { var w = e1(), v = e2(), c = v = --x; return (w = x) - c; }
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function f6(x) { var w = e1(), v = e2(); return (v = --x) - (w = x); }
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function f7(x) { var w = e1(), v = e2(), c = v - x; return (w = x) - c; }
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function f7(x) { var w = e1(), c = e2() - x; return (w = x) - c; }
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function f8(x) { var w = e1(), v = e2(); return (w = x) - (v - x); }
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function f9(x) { var w = e1(); return e2() - x - (w = x); }
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}
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@ -699,7 +699,7 @@ collapse_vars_lvalues_drop_assign: {
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function f4(x) { var a = (x -= 3); return x + a; }
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function f5(x) { var v = (e1(), e2()), c = v = --x; return x - c; }
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function f6(x) { e1(), e2(); return --x - x; }
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function f7(x) { var v = (e1(), e2()), c = v - x; return x - c; }
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function f7(x) { var c = (e1(), e2() - x); return x - c; }
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function f8(x) { var v = (e1(), e2()); return x - (v - x); }
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function f9(x) { e1(); return e2() - x - x; }
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}
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